[A special Guest Blog from Van Air Systems.]
It was the only time a customer has threatened to sue me. His expensive new compressed air dryer wasn’t working correctly. “Get out here now and fix the problem or I call in the lawyers,” he said.
Several days later, I sat in his office at the edge of a sprawled metal refining plant in the western United States, holding the print out of an ugly a dew point log. The data spoke clearly. The equipment my company had manufactured was not performing to specification. My customer had every right to be furious.
Months earlier, we’d supplied a desiccant air dryer sized for 6000 scfm. We designed the dryer to deliver compressed air with a -40⁰ F pressure dew point. But the data my customer now presented showed that each desiccant tower held dew point only for about two hours. Then the dew point climbed ever higher into positive territory, capping at around 20⁰ F before the dryer would switch towers, and the cycle of underperformance would begin again.
Many of those who ask for -40⁰ F dew point compressed air don’t really need it. This customer actually did. He explained how trace amounts of water vapor in his compressed air supply could foul millions of dollars of raw material. No wonder he wanted to sue me!
A colleague and I spent the entire day testing the dryer, tweaking settings, measuring operating conditions, inspecting the pre-filters, condensate drains, and even the air compressors. Nothing seemed wrong. And yet the desiccant beds did not perform. We ended that day feeling defeated, unsure why our equipment wasn’t performing.
We returned the next morning and started troubleshooting once again. I went to inspect the dual oil removing coalescing pre-filters. The redundant filters were housed in a kind of exposed lean-to about 50 feet from the dryer building. Walking toward the lean-to, I passed beneath the 6-in. pipe that linked the filters and dryer. There was a cool breeze. The connecting pipe was exposed to cold ambient air. Suddenly I knew exactly why the dryer wasn’t working and didn’t even bother to take a second look at the filters.
Compressed air traveling in the piping between a coalescing pre-filter and a desiccant dryer is water saturated—or 100% relative humidity. This means any heat loss in the compressed air results in condensation. Normally this is not a meaningful fact, as filters are almost always installed in close proximity to the dryer and minimal heat loss occurs. In this case, the filters were remote and the exposure of the piping to ambient air caused substantial temperature loss. I measured a temperature differential of nearly 4⁰ F between the filters and the dryer inlet. This might seem insubstantial, but I calculated that in this large air system the heat loss was producing just over a gallon per hour of oily condensate!
I presented this hypothesis to the customer: Liquid contamination was shortening the available adsorption time of his desiccant beds. My advice was to move the filters to the within the dryer building and replace the desiccant beds.
A week later we received from the customer a desiccant sample. The normally white beads were brown, supporting my hypothesis of oil contamination.
I took away from this case a few lessons. One, keep your filters near your desiccant dryer. Free liquids are the death knell of desiccant beds. More importantly, I learned the importance of broadmindedness when troubleshooting. The dryer wasn’t working. But that didn’t mean the dryer was broken. Often times, you have to look well beyond the symptom to discover the cure.
The customer never did return my calls to confirm the filters were moved. Then again, I never heard from his lawyers either.
Tyler Currie is the VP of Business Development at Van Air Systems and blogs at vanairsystems.com/blog. Follow Van Air Systems on Twitter at: @air_dryer.
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